porcelain floor tiles plywood ? Advice and information on tiling and fixing tiles to a variety of surfaces

[ajax]

hello,
I am about to have my bathroom floor tiled, and have asked 3 or 4 tilers whether I should put plywood on the floor beneath tiles. I have just had the floor renewed, with the tongue and groove chipboard floor (not waterproofed type) of depth 18mm. There will be 500x500 porcelain tiles going down on the floor. Problem is, everybody seems to give me a different answer, yes, no, 18nn ply, 6mm ply etc... and I am soooo lost know who to go with/beleive.

What should I do/put down ?

many thanks

[Skunkfu]

As far as i understand, your bathroom has 18mm chipboard laid already? Why would you want to lay ply on top? To water proof it and to reinforce the floor i think there is nothing better than "cementboard" from Wickes [its very cheap], just screw sheets directly onto chipboard and tile away!

[ajax]

Hello,

yes, thats correct, its got 18mm new chipboard down already I tried to search for the cementboard at Wickes, but coudnt find it, as not familiar with it - could you tell me some more about it ?

many thanks

[tubbs]

the idea of ply over the wooden sub floor is to take up any movement due to the movement of the property or swell in the wood. 6mm ply is recommended by 90% of tilers. on site projects it is common pratice to lay on 6mm plyboard. remember to fix tiles using a flexable tile adhesive rapid set is best.

[Skunkfu]

Ajax,
Cement board is grey in colour on both sides, its comes in 12mm x 1200mm x 1600mm or something like that and it stinks :lol: It wont stink up all of your bathroom, but if you smell it close you will see it has this specific smell, because of cement? not sure. You should find it in Wickes where all the rest of plasterboards are. Its kinda lightweight, not afraid of water, wont get mould and as hard as cement. And i think its cheaper than ply.

Tubbs is right in a way, but i wouldnt do "common practice" i would do whats best for me and my house i live in.

Link deleted. No externallinks allowed.

Aww... messes up my post now without that link :[

Posted pic directly instead of the link now, i hope it works.

[PST]

Hi Cement boards are made up of cement and fibregalss which gives it its strength , if you are overlaying with this you will need a minimun of 10mm thickness , using a flexible adhesive and grout.
The other 2 ways are to use an 18mm marine plywood overlay , screwed down all over at 300mm centres and using a flexible adhesive and grout.
Or using a highly flexible adhesive like BAL Fast flexible which is a 2 part flexible rubber crumb adhesive and flexible grout.